The present invention relates to an inlet bleed heat system for heating air supplied to a compressor inlet and particularly relates to such system and to methods of fabricating the system at a fabrication site and transporting the system to an electricity generating site.
Inlet bleed heat systems for elevating the temperature of ambient air drawn into the compressor are known. For example, as disclosed in U.S. Pat. No. 6,027,304, issued Feb. 22, 2000, of common assignee herewith, the disclosure of which is incorporated by reference, an inlet bleed heater is disposed in an air duct for supplying heated ambient air to the compressor inlet. The system as disclosed in that patent includes a housing defining a duct in communication at one side with an air filter and noise suppressor and at its opposite side with the compressor inlet. The duct houses a plurality of tubes supplied with heated air, preferably extraction air from the compressor, for elevating the ambient air flowing through the duct to a predetermined temperature. In the system disclosed in that patent, pipe loops in a sinuous configuration interconnect a common manifold which receives the extraction air from the compressor and the tubes disposed in the air inlet duct. The pipe loops extend away from the manifold, are reversely bent to extend over the manifold and then turn substantially 90xc2x0 for connection with the tubes or donwpipes within the air inlet duct. The pipe loops accommodate thermal expansion of the various parts of the inlet bleed heat system.
While the inlet bleed heat system as disclosed in that patent has been in commerce for some time, certain problems have arisen in connection with its transport and assembly at a field site, e.g., an electricity-generation site. Generally, the inlet duct housing, manifold and downpipes or tubes are fabricated at a fabrication site and transported to the power-generation site, where the pipe loops are secured, e.g., by welding, to the manifold and tubes. It will be appreciated that the factory-fabricated portion of the system has large physical dimensions. The height of the unit when loaded on a trailer approximates the clearance available for transport of the unit under bridges. As a consequence, and notwithstanding careful attention to transportation routes, bridges have been struck by the unit due to driver error, inaccurate measurements of the height of the unit on the trailer and inaccurate bridge heights. Further, the pipe loops are assembled to the unit in the field at the power-generation site because they otherwise would extend the height of the unit above the acceptable height dimension. The field assembly of pipe loops require field welding of the pipe loops of the manifold and downpipes or tubes which, in turn requires X-ray inspection of the welds before the unit can be placed into operation. Field assembly time and maintenance of quality during field assembly have increased costs. As a consequence, there has developed a need for an improved inlet bleed heater system, as well as methods of fabricating and transporting the system.
In accordance with a preferred embodiment of the present invention, there is provided an inlet bleed heat system which can be wholly fabricated at a fabrication site and transported to a power-generation site without exceeding and lying well within height and width transportation limitations. To accomplish the foregoing, the inlet bleed heater system comprises a housing defining an inlet air duct for the compressor, a manifold, a plurality of tubes extending into the air duct and a plurality of devices for accommodating thermally induced relative movement between the manifold and downpipes or tubes when in use and which housing will lie within the defined height and width dimensions. Preferably, the manifold and tubes are coupled to one another through bellows arrangements which accommodate such thermally induced relative movement. Thus, a pipe, preferably having a double-bellows arrangement, is interposed between the manifold and each tube in the air inlet duct. It will be appreciated that the bellows accommodates the thermal axial expansion and contraction of the manifold, as well as movement of the tubes relative to the manifold. The pipes with the double bellows arrangement afford direct connections with the donwpipes and eliminate the loops disclosed in U.S. Pat. No. 6,027,304 overlying the manifold.
Additionally, by utilizing a bellows arrangement and fabricating the entirety of the unit at a fabrication site, the conventional field assembly of pipe loops is entirely eliminated. Also, because factory fabrication utilizing the bellows arrangement reduces stresses in the unit, field X-ray inspection of the weld joints at the fabrication site is eliminated, reducing cost and manufacturing time. Further, because the bellows arrangement reduces the overall height of the system, the factory-fabricated unit can be disposed on its side on a flatbed trailer within a predetermined transportation width limitation and transported from the fabrication site to the power-generation site, with greatly increased clearance between the unit on the trailer and any bridges along the route. The reduced envelope of the factory-fabricated unit, moreover, does not require special permits for all loads and generally does not restrict the routes between the fabrication site and power-generation site. That is, by eliminating pipe loops while maintaining their functionality, the unit can be placed on its side on a trailer for transportation having height and width dimensions well within standard height and width limitations for travel over most highways and rods.
In a preferred embodiment according to the present invention, there is provided in inlet bleed heater for a compressor, comprising a housing defining an air inlet duct for delivering ambient air along a flowpath to the compressor, a plurality of tubes in the flowpath of the air inlet duct, the tubes adapted for receiving heated extraction air from the compressor, each tube including a plurality of apertures spaced from one another for discharging the heated air from the tubes into the flowpath for mixing with the ambient inlet air passing the tubes to supply heated air to the compressor, a manifold carried by the housing for supplying the extraction air from the compressor to the tubes, the manifold and each of the tubes being connected to one another by a bellows enabling relative movement between the manifold and the tubes in response to thermally induced forces.
In a further preferred embodiment according to the present invention, there is provided a method of providing an electricity generation site with an inlet bleed heater for heating ambient inlet air to a compressor, the heater including a housing defining an air inlet duct, a plurality of tubes extending into the duct, and a manifold for receiving heated air from a heated air source, comprising the steps of fabricating the duct, tubes and manifold at a fabrication site, interconnecting the tubes and manifold one to the other at the fabrication site with a device for accommodating thermally induced movement of the manifold relative to the tubes and transporting the fabricated inlet heater to the electricity-generating site.